Glucagon-like peptide-1 (hereinafter to be referred to as “GLP-1”) induces numerous biological effects such as stimulating insulin secretion, inhibiting glucagon secretion, inhibiting gastric emptying, inhibiting gastric motility or intestinal motility, enhancing glucose utilization, and inducing weight loss. It is known that GLP-I may further act to prevent the pancreatic β-cell deterioration that occurs as type II diabetes, non-insulin dependent diabetes mellitus (NIDDM), progresses, and to recover insulin secretion by stimulating the production of new β-cells. Particularly, a significant characteristic of GLP-1 is its ability to stimulate insulin secretion without the associated risk of hypoglycemia that is seen when using insulin therapy or some types of oral therapies that act by increasing insulin expression. In addition, GLP-I is very effective in the treatment of type II diabetes because it does not involve side effects, such as the apoptosis and necrosis of pancreatic β-cells, which result from the long-term administration of the blood glucose-lowering drug sulfonylurea and the like.
However, the usefulness of therapy involving GLP-1 peptides has been limited by the fact that GLP-1 is poorly active, and the two naturally occurring truncated peptides, GLP-1(7-37)OH and GLP-1(7-36)NH2, are rapidly cleared in vivo and have extremely short in vivo half lives. Particularly, it is known that endogenously produced dipeptidyl-peptidase IV (hereinafter to be referred to as “DPP-IV”) inactivates circulating GLP-1 peptides by removing the N-terminal histidine (7) and alanine (8) residues and is a major reason for the short in vivo half-life [see O' Harte et al., 2000].
For this reason, various approaches have been attempted either to use DPP-IV inhibitors (P93/01, NVP-LAF237, NVP-DPP728, 815541A, 823093, MK-0431, etc.) to inhibit the degradation of GLP-1, or to use GLP-1 receptor agonists or GLP-1 derivatives (exendin, liraglutide, GLP-1/CJC-1131, etc.) to extend the half life of GLP-1 peptides while maintaining the biological activity or reduce the rate of the removal of GLP-1 peptides from the body.
Also, exendins, another group of peptides that lower blood glucose levels, were suggested for the first time by John Eng (see U.S. Pat. No. 5,424,286, exendin-3 [SEQ ID NO: 1] HSDGTFTSDL SKQMEEEAVR LFIEWLKNGG PSSGAPPPS and exendin-4). Exendin-4 has the following sequence and shows partial sequence similarity (53%) to GLP-1(7-36)NH2 [see Goke et al., 1993].
His 1-Gly-Glu-Gly-The-Phe-The-Ser-Asp-Leu-Ser- Lys 12-Gln-Met-Glu-Glu-Glu-Ala-Val-Arg-Leu-Phe- Ile-Glu-Trp-Leu-Lys27-Asn-Gly-Gly-Pro-Ser-Ser- Gly-Ala-Pro-Pro-Pro-Ser-NH2 (SEQ ID NO: 2: HGEGTFTSDL SKQMEEEAVR LFIEWLKNGG PSSGAPPPS).
Meanwhile, the exendins are blind in the venom of Helodermatidae or beaded lizards. Exendin-3 is present in the venom of Heloderma horridum, the Mexican beaded lizard, and exendin-4 is present in the venom of Heloderma suspectum, the Gila monster. Also, exendin-4 differs from exendin-3 at only positions two and three. It has resistance to degradation by DPP-IV in mammals and has a longer half-life than GLP-1 having a half-life of less than 2 minutes for DPP-IV [see Kieffer T J et al., 1995 ]. The results of in vivo experiments revealed that exendin-4 shows a half-life of 2-4 hours and can reach a sufficient blood level when it is intraperitoneally administered 2-3 times a day [see Fineman M S et al., 2003]. Also, exendin-4 is known to regulate gastric motility, reduce food intake and inhibit plasma glucagon (U.S. Pat. Nos. 6,858,576, 6,956,026 and 6,872,700). With respect to the blood glucose-regulating action of exendin-4, it was reported that, when exendin-4 was administered alone or in combination with an antidiabetic agent (such as sulfonylurea or metformin) far 28 days, it lowered the level of glycosylated hemoglobin (HbA1C) (which means the amount of hemoglobin bound to glucose in blood) to less than 1% [see Egan J M et al., 2003]. Recently, synthetic exendin-4 (commercially available under the trade name of Byetta™) was approved for use by the US FDA.
Meanwhile, vitamins, which are essential nutrients necessary for a variety of biological processes, are involved directly in human metabolism and growth, particularly the production of digestive enzymes, antibodies and fatty acids, and when they are deficient, various diseases occur. However, for humans and mammals, it is necessary to obtain such vitamins from external sources because they have no ability to synthesize vitamins. For this reason, transport systems capable of absorbing such vitamins are very well developed in the human small intestine, and such vitamins are absorbed into various intestinal sites of the human body through a active transport system, a concentration-dependent passive transport system, an intracellular transport system, a receptor-mediated endocytotic pathway or the like depending on various environmental conditions such as concentration or pH. For example, thiamin and niacin are mostly absorbed in the duodenum, and cyanocobalamin is absorbed throughout the small intestines. They have specific transport systems, the most well-known system of which is a Na-dependent multivitamin transport system, which is a biotin transport system, a kind of active transport system. This system is known to be distributed equally in various human organs, such as liver, kidneys or heart, in addition to small intestines. The affinity constant of this system for biotin in small intestines is known to be about 2.6 nM.
Accordingly, the present inventors have conducted studies to develop exendin derivatives specifically modified with biotin at a specific position of exendin, which are highly pure, increase the in vivo residence time of exendin, are easily absorbed through the mucosa and have the pharmacokinetic profiles and pharmacological properties similar to the therapeutic effects of native exendin by injection, as well as a preparation method thereof and a pharmaceutical composition containing the same.